1. Field of the Invention
The present invention relates to a method and apparatus for facilitating the removal of substantially all the bacterially invaded tooth substance in a carious region, e.g., prior to placing a restoration in an affected area (i.e., enamel and dentin) of a tooth. More particularly, the present invention relates to an improved method and apparatus for the luminescent detection of the bacterially invaded tooth substance in a carious region during removal thereof to facilitate removal of substantially all of the bacterially invaded tooth substance, while providing maximum preservation of healthy tooth structure.
2. Description of the Related Art
To effect caries excavation, e.g., prior to positioning a restoration, the dentist must differentiate between carious tooth substance which will be removed and sound tooth substance which will be conserved. Currently several methods of differentiating between carious and non-carious tooth substance are available.
One available method utilizes the hardness differential between carious and non-carious tooth substance. A sharp dental explorer is utilized to probe the tooth substance and to determine if the tissue is soft or hard. Generally the soft tissue is thought to be carious, while the hard tissue is considered to be non-carious. Utilizing this technique is relatively time consuming to implement. Furthermore, this process is inaccurate (due, e.g., to the subjective analysis employed) and can therefore lead to removal of healthy (i.e., non-carious) tooth substance and can also lead to carious substance being overlooked. Additionally, probing the dentin region of the tooth close to the pulp chamber can disadvantageously lead to exposure of the pulp chamber.
Chemomechanical techniques have also been utilized to effect caries removal. Chemomechanical caries removal is effected by first mixing an appropriate compound, i.e., a compound which softens carious tooth substance. After mixing, the compound is emptied into a suitable instrument for application to the affected area of the tooth. Alternatively, the compound could be directly applied to the tooth after mixing. The carious dentin must be thickly covered with the compound and the compound must be left in place for a period of time (e.g., thirty seconds). An instrument is thereafter utilized to scrape out the softened tooth substance. The cavity is wiped clean and caries removal is checked with a probe. The steps of applying the compound and scraping away the softened tooth substance are repeated until the relevant tooth surface feels hard when probed. Finally, the cavity formed by this process may need to be adjusted with a hand or rotating instrument before a restoration may be placed. Clearly, chemomechanical caries removal is relatively time consuming and involves evaluation of caries removal using a sharp probe. As indicated above, differentiation between carious and non-carious tooth substance using a sharp probe is a subjective procedure which can produce inaccurate evaluations, therefore, the dentist may cease applying the operable compound with residual caries remaining.
A further method for distinguishing between carious and non-carious tooth substance during excavation utilizes a dye to facilitate visual differentiation between carious and non-carious tooth substance. In this technique, a dye which colors carious tooth substance, but not sound tooth substance is applied to a tooth which has been dried by compressed air. Since only the external surface of the tooth will be dyed, continuous re-application of the dye is necessary. Furthermore, dyes have been found to inaccurately color non-carious tooth substance, leading to unnecessary removal of sound tooth substance.
Problematically, the above-identified techniques for differentiating between carious and non-carious tooth substance while effecting caries removal, (e.g., to prepare a tooth to receive a restoration) are cumbersome, time consuming, and generally either do not provide for removal of substantially all of the carious tooth substance at an affected site, or may lead to removal of non-carious tooth substance. If all of the carious material is not removed, the bacteria and carious material that remain (i.e., residual caries) can become recurrent caries.
It is known to utilize fluorescence to differentiate between carious and non-carious tooth substance in a laboratory setting. A histological slice of an extracted tooth is made so that tooth fluorescence can be evaluated under a microscope. Furthermore, it is known to evaluate the fluorescence of teeth to identify early caries from outside a tooth utilizing a computational device to evaluate tooth fluorescence in an attempt to evaluate the presence or absence of caries in a tooth. In one known device, a laser diode provides pulsed light to be directed onto the tooth. Fluorescent light stimulated by the light provided by the laser diode is translated through a handpiece for evaluation by a computational device. The computational device is connected to a display utilized to indicate a numerical output based on the emitted fluorescent light.
Additionally, visual inspection of tooth fluorescence in the red region of the spectrum has been proposed to detect early stage caries. This visual detection has been utilized in conjunction with a laser treatment device to remove early stage caries in tooth enamel. This known device utilizes a cutoff wavelength of 620 nm in evaluating tooth fluorescence so that the early stage caries are displayed as bright spots in the red region of the visible spectrum. This known device utilizes an excitation radiation in the spectral range of 360 to 580 nm to cause tooth fluorescence. To effect treatment of early stage caries in tooth enamel, the intensity of radiation of the emitted light (utilized to cause tooth fluorescence) is increased to a sufficiently strong intensity to cause the early stage caries to die out.
Furthermore, attempts have been made to utilize visual inspection of tooth fluorescence for the detection of caries during treatment (i.e., drilling) of a tooth. In procedures of this type, a discrete light source (e.g., an argon laser) is utilized to direct a luminous beam at a tooth during treatment (i.e., drilling) of the tooth. Procedures of this type are difficult to implement because two discrete devices (i.e., the drill and the light source) must be concurrently placed in or near the mouth during treatment. In an effort to simplify use of these devices, a fiber optic lead is sometimes attached to the light source, and a clip is utilized to selectively affix the fiber optic lead to the dental handpiece containing the drill. This arrangement does not overcome the deficiencies of this device, as the dentist must still manipulate two devices (i.e., the laser, and the drill) and, problematically, the connections (e.g., power cords) of these devices may become tangled during treatment. Additionally, the discrete light source of this device is not well balanced and, to the contrary, is relatively weighty at the rear of the device. Therefore this device (i.e., the light source) cannot easily be balanced in the hand nor can this device be manipulated with any degree of precision. The method of caries removal utilized with this device indicates that caries will appear dark during fluorescence of tooth substance and that excavation of the dark areas of a fluorescent tooth should be removed to effect caries removal.
What is needed in the art is an apparatus and method for utilizing visual inspection of the luminescence of the substance of a tooth (e.g., enamel and dentin) during caries removal to facilitate accurate removal of substantially all of the bacterially invaded tooth substance in a carious region during the preparation of a tooth, e.g., for placing a restoration, which apparatus and method is relatively easy to implement.
What is further needed in the art is a method for identifying bacterially invaded tooth substance in a carious region via visual inspection of the luminescence of tooth substance, which method provides a more accurate indication of the bacterially invaded tooth substance in a carious region so that sound tooth substance can be preserved during caries excavation.
The present invention overcomes the above-identified disadvantages of the prior art by providing a dental handpiece housing a light source operable to cause tooth luminescence. The housing of the dental handpiece of the current invention contains both a mechanism for excavating caries (e.g., caries occupying portions of the enamel, the dentin, and the cementum layers of a tooth) as well as a light source and a light guide which directs light operable to cause luminescence of tooth substance (i.e., carious and non-carious tooth substance) onto an area of a tooth to be treated with the mechanism for excavating caries (e.g., a drill head, i.e., the operable end of an oscillating or rotating drill bit utilized to effect caries excavation). In one exemplary embodiment, the light source produces light having a wavelength at or below the lower end of the visible range of the spectrum (e.g., in the blue-violet portion of the visible spectrum). A filter is utilized to allow the dentist to better evaluate the tooth luminescence to determine the presence or absence of caries, as further described below. The present invention overcomes many shortcomings of the prior art by advantageously combining a mechanism for excavating caries with a light source operable to produce tooth luminescence into a single instrument. Furthermore, the method of the present invention provides a more accurate method for determining the presence or absence of caries via tooth luminescence.
According to the method of the present invention, light having a wavelength operable to produce luminescence in tooth substance (e.g., light having a wavelength toward the lower end of the visual spectrum, e.g., in the blue-violet region of the visible spectrum) is projected onto an affected tooth. In one exemplary embodiment, a filter having a cutoff wavelength at the lower end of the green region of the visual spectrum is then utilized to inspect the illuminated area. The carious lesion appears as multiple regions of different colors, including a bright orange-red central region surrounded by an intensely luminescent area appearing green in color and a dark outer ring. According to the method of the present invention, the bright orange-red central region is identified as the bacterially invaded region. The region outside the dark outer ring comprises unaffected tooth substance (e.g., enamel and dentin). The intensely luminescent zone (green in color) intermediate the red-orange central area (i.e., the carious lesion) and the dark outer ring is much brighter than the normal dentin outside the dark outer ring. The central red-orange zone comprises bacterially invaded tooth substance which should be removed, however, the intensely luminescent zone intermediate the dark red-orange central area and the dark outer ring should not be removed. Known methods of utilizing fluorescence of tooth substance to determine carious regions (while treating, i.e., drilling the caries) indicate that dark areas of fluorescent tooth substance should be recognized as carious material and should be removed. Removal techniques of this type would indicate removal to the dark outer ring identified by the present invention, and, therefore, lead to unnecessary removal of non-bacterially invaded tooth substance. With the method of the present invention, a dentist may accurately discern (via visible luminescence) bacterially invaded tooth substance during removal thereof so that healthy tooth substance can be efficiently preserved.
The invention, in one form thereof, comprises a dental handpiece having a housing with a drill head protruding from the housing. The drill head is operably connected to a motor mounted in the housing. A light source is also mounted in the housing and is operable to produce light through an opening in the housing. The opening in the housing is located so that the light produced by the light source is projected substantially in a direction along which the drill head protrudes from the housing. The light has a desired wavelength operable to produce tooth luminescence.
The invention, in another form thereof, comprises a dental handpiece having a housing with excavation means for excavating carious material occupying a portion of a tooth. The dental handpiece further includes illumination means for emitting light of a desired wavelength operable to produce tooth luminescence. The illumination means is mounted in the handpiece housing together with the excavation means. Guide means are utilized to guide an emitted light from the illumination means to an opening in the housing. The opening is located in the housing so that the emitted light is projected onto the tooth when the excavation means is operably positioned for excavating the bacterially invaded region of the tooth.
The apparatus of the present invention may further include filter means for filtering a luminescence of the tooth caused by the light produced by the light source in the dental handpiece. In this form of the current invention, the filter means has a cutoff wavelength whereby the light produced by the light source cannot traverse the filter means. Generally, the filter means only allows light having wavelength between the red and the green region of the visible spectrum to pass. In one exemplary embodiment, the filter has a cutoff wavelength of 500 nm, whereby only light having a wavelength equal to or greater than 500 nm can traverse the filter means. The filter means utilized in accordance with the present invention can include, e.g., colored glass filters, coated glass filters, or mirrors (i.e., dichroic mirrors).
The invention, in another form thereof, comprises a method of identifying a caries in a tooth. The method of this form of the current invention comprises the steps of: projecting a light of desired wavelengths onto the tooth, the light causing a luminescence of the tooth; observing the luminescence of the tooth; identifying a red-orange central region surrounded by an intensely luminescent region and a dark outer ring, whereby the intensely luminescent region is intermediate the red-orange central region and the dark outer ring; and recognizing the red-orange central region as a bacterially invaded region.
An advantage of the present invention is the ability to accurately remove substantially all of the bacterially invaded tooth substance during preparation of a tooth, e.g., to receive a restoration, while avoiding removal of non-bacterially invaded tooth tissue.
Another advantage of the present invention is the provision of a relatively non-cumbersome method and apparatus for effecting removal of substantially all of the bacterially invaded tooth substance at an affected site of a tooth.
Yet another advantage is the ability to decrease the time necessary to effect removal of carious tooth substance relative to conventional techniques. The method of the current invention is relatively efficient compared to conventional techniques because time-consuming changes of instruments and/or concurrent use of multiple instruments, as well as application and re-application of dye is avoided.